18 January 2015
While you image a galaxy, you most likely think about a sleek spiral galaxy. Whereas spiral galaxies are fairly widespread, there are different varieties. When Edwin Hubble first categorized galaxies, he labeled them as spiral, irregular or lenticular. Whereas spirals are the most typical kind of galaxy, the second commonest is lenticular.
In Hubble’s day, some presumed that galaxies started as irregular galaxies, when then collapsed into flat spiral galaxies over time. We now know that isn’t the case. It seems ellipticals start as small spiral galaxies, in early galactic clusters, however frequent collisions stirred them up. As they ran out of fuel and mud to gas star manufacturing and keep their spirals, additional collisions led to their irregular form. Lenticular galaxies share options of each spirals and irregulars. Like spirals they have an inclination to have a central bulge and a flat disk form. Like irregulars they are typically populated by outdated stars. So how did these galaxies type?
In the event that they had been irregular galaxies on the way in which to changing into spirals, one would count on them to have energetic areas of star manufacturing and loads of fuel and mud. However lenticulars don’t have a lot star manufacturing, and whereas they’ve mud, there’s not as a lot as in spiral galaxies. On condition that lenticulars are populated by older stars, it appears that evidently they’re ageing spiral galaxies. As spiral galaxies age, they steadily eat the fuel accessible for star manufacturing. These areas of fuel assist keep the spiral form of the galaxy. However after the fuel is consumed, the spiral arms start to smear out, and the remaining mud tends to comply with round arcs.
So what as soon as appeared like a transition between spiral and irregular galaxies appears to be the form of issues to come back for a lot of spiral galaxies.